MARTIN BUILDERS TYPICAL CONSTRUCTION Crawl Space Houses: The use of 6"X 8" drop sills under the 16" on center floor joists contributes to a very strong and stable floor system which allows you to place furniture (waterbeds, pianos, etc.) as desired. All floor joists, wall framing, ceiling joists, and rafters are spaced 16" on center. Our homes are constructed using wood sheathing on the exterior walls and gable ends of the house whether vinyl or brick. Our roof construction, whether trusses or cut rafters, are spaced 16" on center which contribute to a more level and smoother looking roof than roofs that have a 24" spacing which is typical in a lot of homes.